Lecture 15

Question 1

Strengthing materials

Answer 1

If you can not remove dislocations, then you must make them difficult for them to move in order to increase yield strength. This is done by

• Plastically deforming the material
• Reducing the grain size of the material
• Adding atoms of another element
• Adding particles to the second phase of the metal

Question 2

Strain hardening

Answer 2

Plastic deformation increases the number of dislocations. Dislocation interactions are repulsive. Slip can take place on different planes

Question 3

Cold work

Answer 3

%CW=((Ao-Af)/Ao)*100

Question 4

In polycrystalline materials, dislocation takes place across

Answer 4

the grain boundary.

Question 5

Two crystals either side of the boundary have slip planes

Answer 5

Orientated differently

Question 6

Grain boundaries act as a barrier to dislocation, because

Answer 6

Dislocation passing from one grain to another will have to change direction
Atomic order is disrupted in the grain boundary region